1. Field of the Invention
The present invention relates to a magnetic recording medium and a magnetic recording/reproducing device using the magnetic recording medium.
2. Description of the Related Art
Conventionally, a metallic substrate formed of aluminum alloy or the like is often used as a substrate for a magnetic recording medium. The surface of the metallic substrate is usually textured. Such texturing is a process of forming irregularities along a given direction (usually, along a circumferential direction) on the substrate surface. By performing the texturing, a magnetic film formed on the substrate can be made to have magnetic anisotropy in the circumferential direction, thereby improving magnetic characteristics such as thermal fluctuation resistance and resolution.
In recent years, a nonmetallic substrate formed of glass, ceramic, etc. has been widely used in place of the metallic substrate of aluminum or the like as the substrate for the magnetic recording medium. The nonmetallic substrate has high hardness, so that the medium is hard to be bruised. Furthermore, the nonmetallic substrate has an advantage in glide height characteristic owing to its high surface smoothness. However, it is difficult to sufficiently texture the surface of the nonmetallic substrate such as a glass substrate.
In view of the above problem, it is desirable to improve the magnetic anisotropy of a magnetic film formed on the nonmetallic substrate such as a glass substrate without texturing the substrate surface. A technique of forming an obliquely grown crystal layer on the surface of a nonmetallic substrate has been proposed in Japanese Patent Laid-open No. 2002-203312. In forming the obliquely grown crystal layer, grains grow in a direction inclined from a normal to the substrate surface. Magnetic crystal layers are formed as multiple layers on the upper surface of the obliquely grown crystal layer. According to a magnetic recording medium adopting the obliquely grown crystal layer, the magnetic anisotropy in the circumferential direction of the medium can be improved in the upper magnetic crystal layer. However, a relatively long time is required for the formation of the obliquely grown crystal layer by using a sputtering device, resulting in low productivity.